A typical cylinder block of an engine has a groove-like cooling passage in which cooling heat medium (coolant) flows. For example, in Japanese Laid-Open Patent Publication No. 2000-345838, discloses a cooling structure in which a cooling passage is divided into a plurality of passages in the direction defined by the depth of the passage. This reduces difference in the temperature in the axial direction of each cylinder bore. Specifically, the cooling structure causes a difference in the flow rate of coolant between an upper portion and a lower portion of the cooling passage to decrease the difference in the temperature in the axial direction of each cylinder bore.
In this cooling structure, a highly rigid member formed of, for example, stainless steel forms a partition member that partitions the passage in the axial direction of each cylinder bore. Further, the above-described passage is defined with limited dimension accuracy. Thus, if the partition member must be fitted independently in the passage of the cylinder block, which is formed through casting, it is extremely difficult to arrange the partition member accurately at a desired position in the passage. To solve this problem, in Japanese Laid-Open Patent Publication No. 200-345838, the partition member and a gasket are coupled together through swaging using projecting pieces. In this manner, the partition member is suspended from the gasket at a deck surface of the cylinder block and thus positioned in the axial direction of each cylinder bore.
However, even if positioning of the partition member is accomplished accurately, an edge of the partition member may not be held in tight contact with an inner surface of the passage. In this case, the cooling heat medium may flow through the gap between the partition member and the inner surface of the passage and easily switch between the upper portion and the lower portion of the passage. This reduces the effect of the partition member, which separates the groove-like cooling heat medium passage in the axial direction of each cylinder bore.